Soil Cement

Cement-modified soil (CMS)(Soil Cement) is a subbase solution that blends cement and water with native soils to improve undesirable soil properties. The engineered mix forms a weather-resistant work platform for construction operations and a stronger, permanent subgrade for enhanced pavement support and capacity.

Soil cement is a construction material, a mix of pulverized natural soil with small amount of portland cement and water, usually processed in a tumble, compacted to high density. Hard, semi-rigid durable material is formed by hydration of the cement particles.

Soil cement is frequently used as a construction material for pipe bedding, slope protection, and road construction as a subbase layer reinforcing and protecting the subgrade. It has good compressive and shear strength, but is brittle and has low tensile strength, so it is prone to forming cracks.

Soil cement mixtures differs from Portland cement concrete in the amount of paste (cement-water mixture). While in Portland cement concretes the paste coats all aggregate particles and binds them together, in soil cements the amount of cement is lower and therefore there are voids left and the result is a cement matrix with nodules of uncemented material.

Silt and clay soils, particularly when they are wet, can lead to construction problems. These soils can be soft, plastic, and difficult to compact. Soil Cement is used to improve the engineered properties and construction characteristics of silt and clay soils by reducing this plasticity and enhancing the compaction and strength of the treated soil.

The Process
The amount of cement content needed to modify the in-situ soils is based on the specified level of modification, which is expressed in terms of plasticity, bearing capacity, or other criteria. Portland cement provides all of the compounds and chemistry necessary to improve soils. Cement application rates typically vary from 2 to 5 percent by dry weight of the soil being modified.

Once the cement content has been established, the construction steps are simple and quick:

• Shape the area to the correct crown and grade
• If necessary, pre-wet dry soils to aid pulverization or dry wet soils by aeration
• Spread the cement in either dry form or by slurry method
• Mix with pulverizer, adding water, if necessary, until a homogenous, friable mixture is obtained
• Compact mixed soil to proper density
• Finish by shaping area to final crown and grade